/Engine/Plugins/Online/OnlineSubsystem/Source/Public/Interfaces/OnlineExternalUIInterface.h
Displays a system dialog to purchase user account upgrades. e.g. PlaystationPlus, XboxLive GOLD, etc.
true if it was able to show the UI, false if it failed
bool ShowAccountUpgradeUI ( const [FUniqueNetId](API\Runtime\CoreOnline\Online\FUniqueNetId) & UniqueId )